Using Perl to log transform data

Very simple code using Perl to log transform (base 2) a list of numbers. 0 values are converted into 0.5, since you cannot take the logarithm of 0. For this example numbers are stored in the array @n.

#!/bin/env perl

use strict;
use warnings;

#my list of numbers
my @n= qw/0 2 4 6 8 10 20 40 80 160 320/;

#my log transformed numbers
my @l= log2(@n);
print join("\t", @l), "\n";
#outputs
#-1.00   1.00    2.00    2.58    3.00    3.32    4.32    5.32    6.32    7.32    8.32

exit(0);

sub log2 {
   my @n = @_;
   my @t = ();
   foreach my $n (@n){
      if ($n == 0){
         $n = '0.5';
      }
      my $t = log($n)/log(2);
      #rounded to two decimal places
      $t = sprintf("%.2f",$t);
      push(@t,$t);
   }
   return(@t);
}

Using R

I know this post is about using Perl to log transform data, but I've been using R more and more and it's much easier.

number <- c(0, 2, 4, 6, 8, 10, 20, 40, 80, 160, 320)
number
 [1]   0   2   4   6   8  10  20  40  80 160 320
log2(number)
 [1]     -Inf 1.000000 2.000000 2.584963 3.000000 3.321928 4.321928 5.321928
 [9] 6.321928 7.321928 8.321928
#log base 10
log(base=10, x=number)
 [1]      -Inf 0.3010300 0.6020600 0.7781513 0.9030900 1.0000000 1.3010300
 [8] 1.6020600 1.9030900 2.2041200 2.5051500